Zeolites are alumina silica minerals that contain alkali and alkaline-earth metals, such as sodium, potassium and calcium as well as water molecules within their structural framework. The framework is relatively porous, enclosing inter-connected cavities in which metal cations and water molecules resides.
The cations and water molecules have a considerable freedom of movement within the framework of aluminium, oxygen, and silicon atoms and this gives zeolite cation-exchange and reverse dehydration properties. The porous framework of the zeolites enables them to act as molecular sieves which are able to separate molecular mixtures on the basis of the size and shape of the molecular compounds, or enables the selective absorption of gasses. These unique properties are utilized in diverse industrial processes such as the purification of water and other liquids, purification of gasses, chemical separation, catalysis, and decontamination of radioactive waste.
Synthetic zeolites are synthesized with various organic agents, termed hereinafter "templating agents", which are responsible for the formation of uniform pores in the newly synthesized zeolite crystals. The templating agent act as void fillers and in addition extend the possible range of silica to alumina ratios capable of forming zeolites. The templating agent is strapped, during crystallization within the structure of the zeolite and is then removed by calcination so that only a pore is left where the templating agent was originally trapped. A large number of templating agents are used, among them various organic amines and organic alcohols the most common being tetrapropylammonium bromide (TPA-Br), tetrabutylammonium bromide (TBA-Br)..sup.(1-7)
The excess of the templating agent present in the reaction mixture after the crystallization of the zeolites is discarded as waste. Since the templating agent is the most expensive component in zeolite production, the need to constantly replenish the reaction mixture with large amounts of templating agents after each cycle of zeolite formation considerably raises the cost of production.
Furthermore, most templating agents, such as TPA-Br, are toxic, and consequently due to environmental consideration, have to be disposed utilizing expensive waste-disposal techniques.
It would have been highly desirable to provide a process for production of zeolites which recycles a large percentage of the templating agent. Such a process could decrease the amount of templating agents which has to be added to each cycle of production and consequently considerably lowers the cost of production of zeolites. Furthermore, such a process could minimize the problem of toxic waste.